Klein Marine Systems, Inc. HYDROCHART 3500, Руководство по эксплуатации и обслуживанию

Страница: 65 / 86

A-1
APPENDIX A: S
ONAR
U
NCERTAINTY
M
ODEL
Data acquired by the HydroChart 3500 Sonar System can be post processed using
the Klein Batch Processing GUI (graphical user’s interface) to compute both the
sonar and bathymetry solutions and store the data in either Klein Marine Systems
SDF format or in an industry standard format, such as XYZ or GSF. The Batch
Processing GUI, which is implemented in Klein Marine Systems SonarPro data
acquisition and display software, allows the application of a variety of external
factors, such as vessel geometry, vessel motion, a sound velocity profile, and sonar
calibration, all in a post processing environment. In addition, Klein Marine
Systems has developed and validated a sonar uncertainty model which can be used
during post processing to provide an estimation of the uncertainty in the sonar
depth measurements. The Batch Processing GUI generates the uncertainty
estimates using this model and includes them with the processed data.
A.1 IHO S-44 Uncertainty Definition
As defined by the IHO S-44 standard, the uncertainty for a bathymetric sonar is the
uncertainty of the angle or the depth estimate from the sonar head to the sea floor
at a 95 percent confidence level. These uncertainties are dependent on the
measured receiving angle, the signal-to-noise (SNR) ratio, the wind speed, and the
bottom grain size. When combined with uncertainties from other sensors, such as
an MRU, total uncertainty surfaces of angle and depth estimation can be
generated. This information can be used by the Combined Uncertainty and
Bathymetry Estimator (CUBE) to provide automatic and efficient post processing
of the sonar data and an estimate of the true depth by optimally combining
uncertainties from all of the contributing sources. CUBE is available with
hydrographic survey software.
A.2 Generating the Uncertainty Estimates
To generate the uncertainty estimates, raw sonar data in Klein Marine Systems
SDF format is batch processed in accordance with the selections entered in the
Klein Batch Processing GUI dialog box shown in Figure A-1. The receiving angle
and the SNR are derived from the sonar data, and default settings for wind speed
and grain size are provided; however, known or estimated values for these
parameters can instead be entered manually. The batch processed SDF file
contains the derived SNR values and all the uncertainty data embedded with each
angle solution. To generate an XYZ file, the file option selections are made in the
dialog box shown in Figure A-2. In this case an SNR of 6 dB, a quality factor of
78% and an uncertainty threshold of 10 mrad should be used to start.